The present invention relates to novel prostacyclin analogs and intermediates for their production. In particular, the present invention relates to prostacyclin intermediates useful in the production of 2,5-inter-o-phenylene-3,4-dinor-prostacyclin analogs. Most particularly the present invention provides 2,5-inter-o-phenylene-3,4-dinor-PGF.sub.2 compounds. The preparation and use of the novel compounds is described in Appendix A.